/*
 * Copyright (c) 2011-2015 Pivotal Software Inc., Inc. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *       http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.camunda.bpm.extension.reactor.projectreactor.queue.internal;

/**
 * @author Stephane Maldini
 */

import org.camunda.bpm.extension.reactor.projectreactor.internal.PlatformDependent;

import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;

abstract class MpscLinkedQueueTailRef<E> extends MpscLinkedQueuePad1<E> {

  private static final long serialVersionUID = 8717072462993327429L;

  @SuppressWarnings("rawtypes")
  private static final AtomicReferenceFieldUpdater<MpscLinkedQueueTailRef, MpscLinkedQueueNode> UPDATER;

  static {
    @SuppressWarnings("rawtypes")
    AtomicReferenceFieldUpdater<MpscLinkedQueueTailRef, MpscLinkedQueueNode> updater;
    updater = PlatformDependent.newAtomicReferenceFieldUpdater(MpscLinkedQueueTailRef.class, "tailRef");
    if (updater == null) {
      updater = AtomicReferenceFieldUpdater.newUpdater(
        MpscLinkedQueueTailRef.class, MpscLinkedQueueNode.class, "tailRef");
    }
    UPDATER = updater;
  }

  private transient volatile MpscLinkedQueueNode<E> tailRef;

  protected final MpscLinkedQueueNode<E> tailRef() {
    return tailRef;
  }

  protected final void setTailRef(MpscLinkedQueueNode<E> tailRef) {
    this.tailRef = tailRef;
  }

  @SuppressWarnings("unchecked")
  protected final MpscLinkedQueueNode<E> getAndSetTailRef(MpscLinkedQueueNode<E> tailRef) {
    // LOCK XCHG in JDK8, a CAS loop in JDK 7/6
    return (MpscLinkedQueueNode<E>) UPDATER.getAndSet(this, tailRef);
  }
}
